IMPORTANCE OF ELECTRODE CONDUCTIVE SURFACE-AREA AND EDGE EFFECTS ON VENTRICULAR DEFIBRILLATION EFFICACY

Surface Area, Edge Effects, and Ventricular Defibrillation. Introducti on: The role of edge effects and electrode surface area of the right v entricular (RV) transvenous lead (TVL) on defibrillation efficacy is u nknown. Methods and Results: Defibrillation threshold (DFT) testing wa s conducted randomly in 12 dogs using ring electrode leads in an RV/SV C (superior vena cava) or RV/SVC/patch system, The leads (RV-4, RV-8t, RV-8, RV-15) had electrode surface areas of 20%, 20%, 40%, and 70%, r espectively. A computer model predicted the magnitude of electrode sur face current (RV-8t > RV-4 > RV-8 > RV-15) and the potential distribut ion CPD) at four sites: electrode surface (site a) and at 2 mm (b), 4 mm (c), and 8 mm (d) away from the surface, Despite different near-fie ld PDs (sites a, b, c), PDs mere nearly identical at site d. Resistanc e decreased as the surface area increased. DFT energy for the RV-15 le ad was lower than the RV-4 and RV-8t, There was no difference between energy requirements for the RV-15 and RV-8 leads, No difference was fo und in DFT current for each lead, Comparison of the RV-St and RV-4 lea ds showed no difference in DFT energy despite a lower resistance and a greater number of edges, Conclusions: increasing the RV TVL surface a rea lowered the resistance, However, surface area coverages greater th an or equal to 40% did not lower DFT energy. No significant change ii DFT current occurred despite different predicted near-field current de nsities. PDs were nearly identical 8 mm from the electrode surface, Th us, the far-field current density appears to play a more important rol e in determining defibrillation success.